In their starkest warning yet, following nearly seven years of new research on the climate, the Intergovernmental Panel on Climate Change (IPCC) said it was “unequivocal” and that even if the world begins to moderate greenhouse gas emissions, warming is likely to cross the critical threshold of 2C by the end of this century. That would have serious consequences, including sea level rises, heatwaves and changes to rainfall meaning dry regions get less and already wet areas receive more.

In response to the report, the US secretary of state, John Kerry, said in a statement: “This is yet another wakeup call: those who deny the science or choose excuses over action are playing with fire.”

“Once again, the science grows clearer, the case grows more compelling, and the costs of inaction grow beyond anything that anyone with conscience or commonsense should be willing to even contemplate,” he said.

As their erroneous efforts to discredit the ‘Hockey Stick’ curve reveal, sceptics are tying themselves in knots to maintain denial

The original 1999 Hockey Stick study (and the 2001 Third IPCC Assessment report) concluded that recent northern hemisphere average warmth was likely unprecedented for only the past 1,000 years. The 2007 IPCC Fourth Assessment extended that conclusion back further, over the past 1,300 years (and it raised the confidence to “very likely” for the past 400 years). The new, Fifth IPCC Assessment has now extended the conclusion back over the past 1,400 years. By any honest reading, the IPCC has thus now substantially strengthened and extended the original 1999 Hockey Stick conclusions. [..]

The stronger conclusions in the new IPCC report result from the fact that there is now a veritable hockey league of reconstructions that not only confirm, but extend, the original Hockey Stick conclusions. This recent RealClimate piece summarizes some of the relevant recent work in this area, including a study published by the international PAGES 2k team in the journal Nature Geoscience just months ago. This team of 78 regional experts from more than 60 institutions representing 24 countries, working with the most extensive paleoclimate data set yet, produced the most comprehensive northern hemisphere temperature reconstruction to date. One would be hard-pressed, however, to distinguish their new series from the decade-and-a-half-old Hockey Stick reconstruction of Mann, Bradley and Hughes. [..]

The lesson here, perhaps, is that no misrepresentation or smear is too egregious for professional climate change deniers. No doubt, we will continue to see misdirection, cherry-picking, half-truths and outright falsehoods from them in the months ahead as the various IPCC working groups report their conclusions.

Don’t be fooled by the smoke and mirrors and the Rube Goldberg contraptions. The true take-home message of the latest IPCC report is crystal clear: climate change is real and caused by humans, and it continues unabated. We will see far more dangerous and potentially irreversible impacts in the decades ahead if we do not choose to reduce global carbon emissions. There has never been a greater urgency to act than there is now.

The Intergovernmental Panel on Climate Change is set to issue its strongest warning yet that climate change is caused by humans, and that the world will see more heat waves, droughts and floods unless governments take action to drastically reduce emissions of greenhouse gases. The IPCC report, released every six years, incorporates the key findings from thousands of articles published in scientific journals, concluding with at least 95 percent certainty that human activities have caused most of Earth’s temperature rise since 1950, and will continue to do so in the future. “Drought is the number one threat we face from climate change because it affects the two things we need to live: food and water,” says Jeff Masters, director of meteorology at the Weather Underground. We also speak to Greenpeace International Executive Director Kumi Naidoo.